GmailFS [1] provides a mountable Linux filesystem which uses your Gmail account as its storage medium. GmailFS is a Python application and uses the FUSE userland filesystem infrastructure to help provide the filesystem, and libgmail to communicate with Gmail.
Just be aware what you do, if you use it 😉
[1] http://richard.jones.name/google-hacks/gmail-filesystem/gmail-filesystem.html
Update: More on Google as seen from outside [2].
[2] http://blog.outer-court.com
